diff --git a/src/main/sftp.ts b/src/main/sftp.ts
index b4c17b4..1c319ad 100644
--- a/src/main/sftp.ts
+++ b/src/main/sftp.ts
@@ -325,12 +325,58 @@ export function renameRemote(sessionId: string, from: string, to: string): Promi
   return withSftp(sessionId, sftp => pVoid(cb => sftp.rename(from, to, cb)))
 }
 
+/**
+ * "The file is already gone" — the one server-side failure a delete may treat
+ * as success. ssh2 reports the SFTP status both ways: `code` carries the numeric
+ * status (2 = SSH_FX_NO_SUCH_FILE) and `message` the library's own English text,
+ * so both are checked (builds fill one or the other). Our own translated errors
+ * never reach this check — they arrive as OperationError, which the caller
+ * passes through untouched.
+ */
+function isNoSuchFile(err: unknown): boolean {
+  if ((err as { code?: unknown } | undefined)?.code === 2) return true
+  return /no such file/i.test((err as Error | undefined)?.message ?? '')
+}
+
+/**
+ * unlink/rmdir where "already gone" counts as success.
+ *
+ * Deleting is not idempotent by nature: the entry may have been removed by
+ * someone else between the listing and the click, or the same delete may be run
+ * again after an earlier pass already removed it. Reporting a path that is
+ * verifiably gone as "delete failed" is a fake error — the end state the user
+ * asked for already holds.
+ */
+async function unlinkIfPresent(sftp: SFTPWrapper, path: string): Promise<void> {
+  try {
+    await pVoid(cb => sftp.unlink(path, cb))
+  } catch (err) {
+    if (!isNoSuchFile(err)) throw err
+  }
+}
+
+async function rmdirIfPresent(sftp: SFTPWrapper, path: string): Promise<void> {
+  try {
+    await pVoid(cb => sftp.rmdir(path, cb))
+  } catch (err) {
+    if (!isNoSuchFile(err)) throw err
+  }
+}
+
 async function deleteRecursive(sftp: SFTPWrapper, path: string, isDir: boolean): Promise<void> {
   if (!isDir) {
-    await pVoid(cb => sftp.unlink(path, cb))
+    await unlinkIfPresent(sftp, path)
     return
   }
-  const names = await readdir(sftp, path)
+  let names: string[]
+  try {
+    names = await readdir(sftp, path)
+  } catch (err) {
+    // The directory is gone (removed by someone else, or by an earlier pass of
+    // this same delete): everything inside went with it, so the intent holds.
+    if (isNoSuchFile(err)) return
+    throw err
+  }
   const base = path.replace(/\/+$/, '') || '/'
   for (const name of names) {
     const child = `${base}/${name}`
@@ -342,7 +388,7 @@ async function deleteRecursive(sftp: SFTPWrapper, path: string, isDir: boolean):
     }
     await deleteRecursive(sftp, child, childIsDir)
   }
-  await pVoid(cb => sftp.rmdir(path, cb))
+  await rmdirIfPresent(sftp, path)
 }
 
 export function deleteRemote(sessionId: string, paths: string[]): Promise<void> {
@@ -354,7 +400,7 @@ export function deleteRemote(sessionId: string, paths: string[]): Promise<void>
         try {
           isDir = (await lstat(sftp, path)).isDirectory()
         } catch {
-          // stat failed — fall through to unlink
+          // stat failed — fall through to unlink, which tolerates "already gone"
         }
         await deleteRecursive(sftp, path, isDir)
       } catch (err) {
diff --git a/src/main/sysinfo.ts b/src/main/sysinfo.ts
index b5351dd..623bc3c 100644
--- a/src/main/sysinfo.ts
+++ b/src/main/sysinfo.ts
@@ -157,7 +157,17 @@ function pollOnce(id: string, state: PollState): void {
 
   try {
     client.exec(COLLECT_CMD, (err: Error | undefined, stream) => {
-      if (state.stopped) return
+      if (state.stopped) {
+        // Polling stopped while this exec was in flight: the channel is already
+        // open, so simply dropping the stream would leak it for the rest of the
+        // ssh session. Close it (best effort — it may be dead already) and go.
+        try {
+          stream?.close()
+        } catch {
+          // best effort
+        }
+        return
+      }
       if (err || !stream) {
         handleError(id, state, err?.message || t('main.sysinfo.execFailed'))
         return
diff --git a/src/main/zmodem.ts b/src/main/zmodem.ts
index 36b4b7d..4c60b14 100644
--- a/src/main/zmodem.ts
+++ b/src/main/zmodem.ts
@@ -65,6 +65,19 @@ export interface ZmodemDeps {
   toTerminal(sessionId: string, data: Buffer): void
   /** Write bytes out to the ssh stream (zmodem frames + CAN abort sequence). */
   writeStream(sessionId: string, data: Buffer): void
+  /**
+   * Backpressure over the ssh stream that FEEDS this session's sentry. pty.ts
+   * owns that channel and injects these two, mirroring writeStream: the engine
+   * has no handle on it, and pausing the source is the only thing that bounds
+   * how much a peer can push into a file sink that is over its highWaterMark.
+   *
+   * Optional so a harness with no real stream still runs (and so an injector
+   * that predates this hook keeps working): without it a backed-up sink still
+   * stops counting progress, which turns a wedged disk into a stall-watchdog
+   * failure instead of an unbounded queue — but the queue itself stays.
+   */
+  pauseSource?(sessionId: string): void
+  resumeSource?(sessionId: string): void
 }
 
 interface Engine {
@@ -94,7 +107,18 @@ interface Engine {
   offerTimer: NodeJS.Timeout | null
   stallTimer: NodeJS.Timeout | null
   receiveStream: Writable | null
+  /**
+   * Octets the current file's sink ACCEPTED. A write that only landed in the
+   * WriteStream's own queue (write() returned false) is not counted here until
+   * the queue drains — see pendingBytes and the receive on_input.
+   */
   bytes: number
+  /** Octets handed to a backed-up sink; folded into `bytes` on drain/teardown. */
+  pendingBytes: number
+  /** True while the source is paused because the sink is over its highWaterMark. */
+  sourcePaused: boolean
+  /** One-shot: the injector supplied no pauseSource, so the pause is a no-op. */
+  warnedNoSource: boolean
   totalBytes: number
 }
 
@@ -176,6 +200,9 @@ function finalize(
   // mistaken for a clean finish.
   engine.ending = true
   cancelTimers(engine)
+  // A pause must never outlive its transfer: the 'drain' that would lift it may
+  // still be queued, or may never come at all once the sink is ending here.
+  releaseSource(engine)
   const stream = engine.receiveStream
   engine.receiveStream = null
   // Clear the slot *before* end(): an errored/destroyed sink must not be ended
@@ -235,6 +262,58 @@ function touchActivity(engine: Engine): void {
   engine.stallTimer = timer
 }
 
+/**
+ * Stop the ssh stream that feeds this engine (receive path only: the send path
+ * pushes into the sink instead of pulling from the peer).
+ *
+ * Idempotent — every subpacket of a blocked window arrives through the same
+ * on_input, and pausing an already-paused channel is pointless work on the hot
+ * path. The flag is set even when the injector supplied no hook, so the
+ * accounting below stays consistent either way.
+ */
+function pauseSource(engine: Engine): void {
+  if (engine.sourcePaused) return
+  engine.sourcePaused = true
+  if (!engine.deps.pauseSource) {
+    // Say it once per transfer instead of silently doing nothing: the hook is
+    // the whole mechanism, so an injector that forgot it still has an unbounded
+    // sink queue (only the progress accounting below improves).
+    if (!engine.warnedNoSource) {
+      engine.warnedNoSource = true
+      console.warn('[zmodem] receive sink is over its highWaterMark but no pauseSource hook was injected')
+    }
+    return
+  }
+  try {
+    engine.deps.pauseSource(engine.id)
+  } catch {
+    // the stream may already be gone
+  }
+}
+
+/**
+ * Undo a backpressure pause, folding the octets that only ever reached the
+ * sink's queue into the received count.
+ *
+ * Called from the sink's 'drain' AND from every teardown path: a pause that
+ * outlived its transfer would leave the session's ssh stream stopped for good
+ * (terminal output and the peer both look frozen, with no way back), and
+ * waiting for a 'drain' that never comes — dead disk, destroyed stream — is
+ * exactly how that happens. Returns whether a pause was actually outstanding.
+ */
+function releaseSource(engine: Engine): boolean {
+  if (!engine.sourcePaused) return false
+  engine.sourcePaused = false
+  engine.bytes += engine.pendingBytes
+  engine.pendingBytes = 0
+  try {
+    engine.deps.resumeSource?.(engine.id)
+  } catch {
+    // the stream may already be gone
+  }
+  return true
+}
+
 function wireSession(engine: Engine): void {
   const session = engine.session
   if (!session) return
@@ -383,23 +462,40 @@ function handleOffer(engine: Engine, offer: Zmodem.Offer): void {
     finalize(engine, false, err instanceof Error ? err.message : t('main.zmodem.receiveFailed'))
   })
 
+  // Backpressure release. The sink's queue is empty again, so the octets that
+  // were parked there are really written, the peer may push more, and this is
+  // the ONLY progress signal while blocked — it must therefore also reset the
+  // stall watchdog (a slow but working disk is not a stalled transfer).
+  stream.on('drain', () => {
+    if (engine.receiveStream !== stream) return
+    if (releaseSource(engine)) touchActivity(engine)
+  })
+
   offer
     .accept({
       on_input: (payload: Uint8Array | number[]) => {
         // zmodem.js delivers the payload as a plain octet Array (not a
         // Uint8Array); coerce defensively to a Buffer before writing.
         const buf = Array.isArray(payload) ? Buffer.from(payload) : Buffer.from(payload.buffer, payload.byteOffset, payload.byteLength)
-        if (!stream.destroyed && !stream.closed) {
-          stream.write(buf)
+        const writable = !stream.destroyed && !stream.closed
+        if (writable && stream.write(buf)) {
+          engine.bytes += buf.byteLength
+          // Not throttled: the stall watchdog measures byte progress, not UI events.
+          touchActivity(engine)
+        } else if (writable) {
+          // write() === false: the sink is over its highWaterMark, so these
+          // octets only sit in Node's queue — for a 100MB file into a slow disk
+          // the whole file would end up there. Pausing the ssh stream makes the
+          // peer wait instead; counting the bytes or touching the watchdog now
+          // would report progress for data that has not reached the disk yet.
+          engine.pendingBytes += buf.byteLength
+          pauseSource(engine)
         }
-        engine.bytes += buf.byteLength
         emitProgressThrottled(engine, {
           file: name,
           bytes: engine.bytes,
           totalBytes: engine.totalBytes
         })
-        // Not throttled: the stall watchdog measures byte progress, not UI events.
-        touchActivity(engine)
       }
     })
     .then(() => {
@@ -521,6 +617,9 @@ export function attachZmodem(sessionId: string, deps: ZmodemDeps): void {
     stallTimer: null,
     receiveStream: null,
     bytes: 0,
+    pendingBytes: 0,
+    sourcePaused: false,
+    warnedNoSource: false,
     totalBytes: 0
   }
   engines.set(sessionId, engine)
@@ -683,6 +782,10 @@ export function detachZmodem(sessionId: string): void {
   if (engine.active) {
     finalize(engine, false, t('main.zmodem.sessionClosed'), 'cancelled')
   }
+  // The engine is about to be dropped: a pause still outstanding here would
+  // never be lifted (finalize already released the active one; this covers the
+  // path where it was not active).
+  releaseSource(engine)
   engine.active = false
   cancelTimers(engine)
   const stream = engine.receiveStream
diff --git a/tests/sftp-timeout.mjs b/tests/sftp-timeout.mjs
index 5b66d9f..f0b6249 100644
--- a/tests/sftp-timeout.mjs
+++ b/tests/sftp-timeout.mjs
@@ -51,8 +51,9 @@ sftp.setLocalPathPolicy({
 /**
  * A fake ssh2 SFTPWrapper whose per-call behavior is scripted.
  * `behaviour(op, args)` returns `'silent'` (never calls back — the dead-channel
- * case), `'error'` (calls back with an error), or `'ok'` (calls back with
- * `result`). Every call is recorded so the test can assert on what was opened.
+ * case), `'enoent'` (calls back with the server's "no such file"), `'error'`
+ * (calls back with a generic error), or `'ok'` (calls back with `result`). Every
+ * call is recorded so the test can assert on what was opened.
  */
 const defaultStat = () => ({
   isDirectory: () => false,
@@ -63,6 +64,9 @@ const defaultStat = () => ({
   gid: 1000
 })
 
+/** SSH_FX_NO_SUCH_FILE as ssh2 surfaces it: a numeric status on an Error. */
+const noSuchFile = () => Object.assign(new Error('No such file'), { code: 2 })
+
 let calls
 let behaviour
 let openedChannels
@@ -101,6 +105,7 @@ const makeWrapper = () => {
     calls.push({ op, args })
     const verdict = behaviour(op, args)
     if (verdict === 'silent') return
+    if (verdict === 'enoent') return cb(noSuchFile())
     if (verdict === 'error') return cb(new Error(`${op} failed`))
     cb(null, voidResult ? undefined : result)
   }
@@ -433,6 +438,77 @@ console.log('default budgets are sane relative to each other')
   ok(elapsed < 3000, `the check itself was quick (${elapsed}ms)`)
 }
 
+// ---- 7. a delete is idempotent: "already gone" is success ------------------
+console.log('deleting an entry that is already gone succeeds instead of reporting a failure')
+{
+  // The file may have been removed by someone else between the listing and the
+  // click, or the same delete may be run again after an earlier pass already
+  // removed it. "No such file" means the end state the user asked for already
+  // holds, so it must not surface as "delete failed".
+  reset((op) => (op === 'lstat' || op === 'unlink' ? 'enoent' : 'ok'))
+  sftp.closeSftp('del-gone')
+  const missing = await expectReject(sftp.deleteRemote('del-gone', ['/remote/gone.txt']), 'deleteRemote')
+  ok(!missing.rejected, `a missing file is not a delete failure (${missing.message})`)
+
+  // The tolerance is for that one status only: a real unlink failure still has
+  // to reach the user.
+  reset((op) => (op === 'unlink' ? 'error' : 'ok'))
+  sftp.closeSftp('del-denied')
+  const denied = await expectReject(sftp.deleteRemote('del-denied', ['/remote/x.txt']), 'deleteRemote')
+  ok(denied.rejected, 'a genuine unlink failure is still reported')
+
+  // The other shape of the same status: no numeric code, only the library's
+  // English message.
+  reset(() => 'ok')
+  sftp.registerSftpClientProvider(() => ({
+    sftp: (cb) => {
+      const w = makeWrapper()
+      w.unlink = (p, cb) => {
+        calls.push({ op: 'unlink', args: [p] })
+        cb(new Error('No such file'))
+      }
+      openedChannels.push(w)
+      cb(null, w)
+    }
+  }))
+  sftp.closeSftp('del-gone-msg')
+  const byMessage = await expectReject(sftp.deleteRemote('del-gone-msg', ['/remote/gone.txt']), 'deleteRemote')
+  ok(!byMessage.rejected, `the message-only form is tolerated too (${byMessage.message})`)
+
+  // The recursive shapes: the directory itself is gone, and a tree whose entries
+  // were already removed reports the same status from unlink and rmdir.
+  reset((op, args) => (op === 'readdir' && args[0] === '/remote/dir' ? 'enoent' : 'ok'))
+  sftp.registerSftpClientProvider(() => ({
+    sftp: (cb) => {
+      const w = makeWrapper()
+      // Only the top-level path is a directory, or the children would recurse.
+      w.lstat = (p, cb) => {
+        calls.push({ op: 'lstat', args: [p] })
+        cb(null, { ...defaultStat(), isDirectory: () => p === '/remote/dir' })
+      }
+      openedChannels.push(w)
+      cb(null, w)
+    }
+  }))
+  sftp.closeSftp('del-dir-gone')
+  const dirGone = await expectReject(sftp.deleteRemote('del-dir-gone', ['/remote/dir']), 'deleteRemote')
+  ok(!dirGone.rejected, `a directory that no longer exists is not a failure (${dirGone.message})`)
+
+  reset((op) => (op === 'unlink' || op === 'rmdir' ? 'enoent' : 'ok'))
+  sftp.closeSftp('del-dir-partial')
+  const dirPartial = await expectReject(sftp.deleteRemote('del-dir-partial', ['/remote/dir']), 'deleteRemote')
+  ok(!dirPartial.rejected, `a tree whose entries were already removed is not a failure (${dirPartial.message})`)
+
+  // Restore the standard provider for any later section.
+  sftp.registerSftpClientProvider(() => ({
+    sftp: (cb) => {
+      const w = makeWrapper()
+      openedChannels.push(w)
+      cb(null, w)
+    }
+  }))
+}
+
 // ---- helpers ----------------------------------------------------------------
 function waitFor(pred, timeoutMs) {
   return new Promise((resolve) => {